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A pot experiment was carried out to investigate the tolerance of cucumber plants (Cucumis sativus L.) to root-knot nematode after inoculation with Glomus intraradices. Plants were inoculated with G. intraradices for four weeks and then transplanted in soil treated with Meloidogyne incognita for a further five weeks. The low phosphorus (P) loamy soil was amended with 50 and 100 mg P kg-1 soil. Mycorrhizal colonization increased shoot dry weight, shoot length, leaf numbers, root fresh weight and shoot P concentration, whereas nematode penetration and reproduction were significantly decreased. Similarly, P fertilization usually increased shoot growth and significantly decreased the number of galls and the number of egg masses and eggs per g root. Our results indicate that inoculation with G. intraradices and P fertilizer confer tolerance of cucumber plants to M. incognita by enhancing plant growth and by suppressing reproduction and/or galling of nematodes during the early stages of plant growth. [ABSTRACT FROM AUTHOR]

A pot experiment investigated the response of two maize inbred lines with contrasting root morphology and phosphorus (P) efficiency to inoculation with Glomus mosseae or Glomus etunicatum compared with non-mycorrhizal controls. Soil phosphorus was supplied at rates of 10, 50, and 100 mg P kg -1 soil. Root length, specific root length, and specific phosphorus uptake of maize line 178 (P-efficient) were significantly higher than of line Hc (P-inefficient). Percentage of root length colonized showed the opposite trend regardless of soil P supply level. The two maize lines did not differ significantly in growth response to mycorrhizal colonization. Root colonization rate decreased with increasing soil phosphorus supply. The beneficial effect of the two AM fungi on plant growth and P uptake was greatest at low soil P level and the responses were negative at high P supply. Mycorrhizal responsiveness also decreased with increasing P supply and differed between the two mycorrhizal fungal isolates. [ABSTRACT FROM AUTHOR]

Three ectomycorrhizal fungal isolates, Cenococcum geophilum SIV, a putative isolate of Pisolithus microcarpus and a Pisolithus sp., were cultured in vitro without potassium (K) and with three levels of K supply (as K2SO4). Some growth stimulation by K was observed among the fungi. Potassium in the liquid medium led to increased concentrations of nitrogen (N) and K in the fungi compared to K-free controls, and to higher phosphorus (P) concentrations in Pisolithus sp., but lower P in C. geophilum SIV. In a second experiment, the K influx rates of the fungi from external solutions followed Michaelis-Menten kinetics, indicating that K influx was an active process. Mycorrhizal fungi showed quite small Cmin values for K influx, ranging from 2.12 to 5.39 µmol L-1, in relation to K concentrations in the external solution. Such low Cmin values might allow the external hyphae to extract K efficiently from K-deficient soils. Furthermore, the fungi had low Km values for K uptake (<14.85 µmol L-1), indicating high affinities and efficiencies of K carriers. Both Pisolithus sp. and P. microcarpus exhibited similar Cmin and Km values but were different from C. geophilum SIV. Furthermore, Imax values varied significantly among the fungi, ranging from 9.60 to 21.63 µmol g-1 DM h-1, perhaps due to variation in the intracellular K concentrations in the ectomycorrhizal fungi. [ABSTRACT FROM AUTHOR]

Three wheat (Triticum aestivum L.) genotypes with high, intermediate and low phosphorus (P) efficiency were grown in a pot experiment with low P supply and adequate P supply either inoculated with the arbuscular mycorrhizal fungus Glomus versiforme or uninoculated. The mycorrhizal dependency of the genotype with relatively high P efficiency was lower than that of the genotypes with lower P efficiencies. Linear correlation analysis revealed that mycorrhizal dependency was primarily controlled by P uptake efficiency. More carbohydrate was translocated to the roots of genotypes with low P efficiency than of those with high P efficiency. In a second pot experiment the same three genotypes were grown in low P soils. Higher hyphal length density arising from carbohydrate translocation led to more P uptake, and this may account for higher mycorrhizal dependency. [ABSTRACT FROM AUTHOR]